Chemical Kinetics Test

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Chemical Kinetics Test - 27

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Weekly Quiz Competition

Question 1
1 / -0

The incorrect statement is:

A
all the collisions between reactant molecules do not lead to a chemical change

B
a zero order reaction proceeds at a constant rate independent of concentration or time

C
fast reactions have low activation energies

D
in a first order reaction, the reaction ideally takes finite time to be completed

Solution

For a reaction to take place, the reacting molecules must colloid together but only those collisions, in which colliding molecules possess certain minimum energy is called threshold energy.
Zero-order reaction, $$rate = k[A]^0 = k$$
So, a zero order reaction proceeds at a constant rate independent of concentration or time.
Every first reaction takes infinite time for completion.
Question 2
1 / -0

A first order reaction has a rate constant $$1.5\times10^{-3}\:sec^{-1}$$. How long will 5.0 g of this reactant take to reduce to 1.25 g.

A
924 sec

B
462 sec

C
1848 sec

D
none of these

Solution

As we know, for a first order reaction,
$$t_{1/2} = 0.693/k$$ and time taken for $$5$$ gm to reduce to $$1.25$$ gm is
$$t = 2t_{1/2} = 2\times 0.693/1.5\times 10^{-3} = 924$$ sec
Question 3
1 / -0

In a zero order reaction half life is 100 sec. After how much time 78 fraction of reactant will be reacted?

A
300 sec

B
200 sec

C
175 sec

D
25 sec

Solution

using the formula for half life time and final concentration, substituting the values doesn't require initial concentration , its gets cancel out giving us the final answer.
Question 4
1 / -0

The rate constant for a zero order reaction is $$2\times10^{-2}\:mol\:L^{-1}\:sec^{-1}$$, if the concentration of the ractant after $$25 sec$$ is $$0.25 M$$, calculate the initial concentration.

A
$$0.75 M$$

B
$$1.5 M$$

C
$$0.375$$

D
None of these

Solution

using the above formula we can get $$ {A}_{0} $$ . given the values of K and $$ {\epsilon} $$ in the question.
Question 5
1 / -0

The half-life period of a first order reaction is $$15\: minute.$$ How much reaction will be completed in $$30\:minute$$?

A
$$\;75\%$$

B
$$\;80\%$$

C
$$\;95\%$$

D
$$\;100\%$$

Solution

$$75\%$$ completion time
$$=T = 2t_{1/2} = 30$$ min as $$t_{1/2} = 15$$ min
Reaction will complete $$75\ %$$ in $$30$$ min only.
Question 6
1 / -0

In a first order reaction the concentration of reactant decreases from 800 $$mol/dm^3$$ to $$50 mol/dm^3$$ in $$2\times 10^4 sec$$. The rate constant of reaction in $$sec^{-1}$$ is:

A
$$2\times 10^{4}$$

B
$$3.415\times 10^{-5}$$

C
$$1.386\times 10^{-4}$$

D
None of these

Solution

As we know,

$$t=\dfrac {2.303}{k} log \left(\frac {N_0}{N}\right)$$

$$k=\dfrac {2.303}{2\times 10^{4}}log \left(\dfrac {800}{50}\right)=1.386\times 10^{-4} sec^{-1}$$
Question 7
1 / -0

A reaction which is of first order w.r.t reactant $$A$$, has a rate constant $$6$$ $${min}^{-1}$$. If we start with $$[A]=0.5mol$$ $${L}^{-1}$$, when would $$[A]$$ reach the value of $$0.05 mol$$ $${L}^{-1}$$?

A
$$0.384min$$

B
$$0.15min$$

C
$$3min$$

D
$$3.84min$$

Solution

As we know, for a first order reaction,

$$t=\cfrac{2.303}{k}\log{\cfrac{a}{a-x}}$$

By putting values, we get
$$t=\cfrac{2.303}{6}\log{\cfrac{0.5}{0.05}}=0.384$$ min
Question 8
1 / -0

For the reaction: $${H}_{2}+{Cl}_{2}\overset { sunlight }{ \longrightarrow}2HCl$$ the order of reaction is :

A
$$0$$

B
$$2$$

C
$$1$$

D
$$3$$

Solution

The reaction is zero order reaction. The order of all photochemical reactions is zero as it does not depend upon the concentration of reactants.
Question 9
1 / -0

A mixture of 2 gases -A (reactive) and X (inert) is kept in a closed flask when A decomposes as per the following roaction at 500 k
$$\displaystyle A(g)\rightarrow 2B(g)\rightarrow 2B(g)+3C(\varphi )+4D(s)$$
$$\displaystyle P^{\circ}=210mm Hg$$
$$\displaystyle P_{t}(10\, mins)=330mm\, Hg$$
$$\displaystyle P_{\infty t}=430mm\, Hg$$
Vapour pressure of $$\displaystyle C(\varphi )$$ at 500 K is 20 mm Hg
Calculate the half-life of A ?

A
5 mins

B
10 mins

C
12 mins

D
Given data is not sufficient to answer
Question 10
1 / -0

When sugar is stirred with a spoon in a glass of water, more sugar is dissolved and faster. Why?

A
Spoon acts as a catalyst

B
On stirring, temperature increases

C
Stirring increases the rate of interaction

D
Spoon increases the attraction between the molecules of water and sugar

Solution

When sugar is stirred with a spoon in a glass of water, more sugar is dissolved and faster because stirring increases the rate of interaction between the molecules of water and sugar due to their increased kinetic energy.

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Re-Attempt Weekly Quiz Competition

Chemical Kinetics Test - 27

Result

Chemical Kinetics Test - 27

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SHARING IS CARING

Question 1

all the collisions between reactant molecules do not lead to a chemical change

a zero order reaction proceeds at a constant rate independent of concentration or time

fast reactions have low activation energies

in a first order reaction, the reaction ideally takes finite time to be completed

Solution

Question 2

924 sec

462 sec

1848 sec

none of these

Solution

Question 3

300 sec

200 sec

175 sec

25 sec

Solution

Question 4

$$0.75 M$$

$$1.5 M$$

$$0.375$$

None of these

Solution

Question 5

$$\;75\%$$

$$\;80\%$$

$$\;95\%$$

$$\;100\%$$

Solution

Question 6

$$2\times 10^{4}$$

$$3.415\times 10^{-5}$$

$$1.386\times 10^{-4}$$

None of these

Solution

Question 7

$$0.384min$$

$$0.15min$$

$$3min$$

$$3.84min$$

Solution

Question 8

$$0$$

$$2$$

$$1$$

$$3$$

Solution

Question 9

5 mins

10 mins

12 mins

Given data is not sufficient to answer

Question 10

Spoon acts as a catalyst

On stirring, temperature increases

Stirring increases the rate of interaction

Spoon increases the attraction between the molecules of water and sugar

Solution

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